Evolutionary Theory and Foundations in Biological Anthropology

Science: Definition and Methodology

• Science is a body of knowledge and a methodology for inquiry.
• It is typically characterized as hierarchical and progressive/incremental in its advances.

Historical Overview: Pioneer Figures in Biological Anthropology

• Johann Friedrich Blumenbach (1752–1840)
  • Promoted static types that supposedly did not change over time.
  • Instrumental in creating five racial categories based on skull studies (craniometry).
  • Helped popularize the idea that human variation falls into categorical races.
• Samuel Morton (1799–1851)
  • Father of physical anthropology in the U.S.
  • Expanded Blumenbach’s racial framework by collecting and measuring over 1,000 crania.
  • Published Crania Americana (1839), detailing methods to measure skull landmarks and cranial capacity (braincase volume).
• Franz Boas (1858–1942)
  • “Father of American Anthropology.”
  • Challenged scientific racism and taxonomy-based views of human variation.
  • Proponent of cultural relativism.
• Aleš Hrdlička (1869–1943)
  • Founder of the American Journal of American Anthropology (1918) and the American Association of Physical Anthropology (1930).
  • Studied skeletons to understand disease impacts; curator of Physical Anthropology at NMNH (1904).
• Earnest Hooton (1887–1954)
  • Emphasized racial classification.
  • Studied convicted criminals for clues about behavior; trained many prominent anthropologists.
  • Influenced the field; Harvard professor and directed the Peabody Museum.
• Sherwood Washburn (1911–2000)
  • “New Physical Anthropology.”
  • Studied non-human primates; refocused research toward evolution, dynamics, and adaptation integrated with evolutionary biology.

Lasting Impacts and Case Study

• In 2022, skeletal remains from Lisht (Egypt) were studied, including Senebtisi (a known individual).
  • Met researchers at the Peabody Museum of Archaeology and Ethnology.
  • Remaining skeletal remains were sent to the National Museum of Natural History.

Debates: Hooton vs. Hrdlička (Lisht Case)”

• Hooton (Peabody):
  • Requested hair-preserved/mummified remains; examined Senebtisi’s skull while ribs and other fragments were not emphasized.
• Hrdlička (NMNH):
  • Studied skeletal remains to understand admixture in ancient Egyptians; noted 92.6% of Lisht remains were disarticulated.

The Conversation: Rights of the Dead and the Living

• A public article discussing equitably handling skeletal remains in research.
• Highlights issues such as who gets to decide for the dead (e.g., mummy owners) and the rights of living communities.
• Emphasizes tension between academic rigor, journalistic integrity, and ethical considerations in handling human remains.

Multi-media Analysis: Focus Questions

• Where were skeletal remains coming from in these articles?
• How do these articles highlight changes to our understanding of human remains over the last century?
• Do the articles discussed change your view of biological anthropology?
• Multi-media Analysis #1 requirements (due Aug 28, Midnight):
  • 1) Who is the author(s)?
  • 2) Who is the intended audience?
  • 3) How do these articles relate to our discussion on Tuesday (8/26)?
  • 4) Provide two questions the articles prompted for you.

Check-in: What Does Evolution Mean to You? (Check-in Question)

• A prompt to reflect personally on evolution and its meaning.
• Check-in questions and class policies (e.g., 3 lowest grades dropped; attendance).

Core Definitions: Evolution and Origins

• Evolution:
  • Definition: Change in allele frequency within a population over time.
  • Notation: allele frequencies p, q; over time t, pt, qt.
  • Change: riangle p = p{t+1} - pt
• Origins: Early concepts and ladder theories
  • Scalae Naturae (Ladder of Being): idea of hierarchical organization of life.
  • Ideal forms vs. real-world variation.

Creationism and Alternative Views

• Creationism: God formed the world and life; often portrays recent creation with little change since.
• This contrasts with evolutionary thought, which emphasizes change over deep time.

Stratigraphy and Uniformitarianism (Geology as Context for Biological Thought)

• Uniformitarianism: The principle that natural processes acting in the present operated similarly in the past.
  • Proponent: James Hutton.
  • Example: Erosion and landform formation are ongoing processes that explain geological history.
• Stratigraphy: The order and relative positions of strata and their relation to geological time.
  • Time scale references (selected):
  • Holocene ≈ 10{,}000 years ago to present
  • Cenozoic era including Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Holocene
  • Major boundaries: K/T boundary, major extinction events at the end of the Cretaceous, etc. (see slide for specific numeric marks)
• Catastrophism (contrast): Doctrine that catastrophic events, not gradual evolution, drive major geological changes.
  • Georges Cuvier identified unknown fossils and concluded extinctions due to catastrophes.

Foundational Biogeography and Taxonomy (Pre-Darwinian Thought)

• John Ray (1627–1705): Father of Natural History; grouped species into species and genera.
• Carolus Linnaeus: Binomial nomenclature; hierarchical classification; example Homo sapiens.
• Early taxonomy and classification schemes (binomial nomenclature, Latin naming).

Early Evolutionary Ideas (Pre-Darwin)

• Georges-Louis Leclerc, Comte de Buffon (1707–1788)
  • Argued against fixity of species; organisms are adapted to their environment.
  • Did not have a mechanism for how change occurs.
• Erasmus Darwin (1731–1802) and Robert Chambers (1802–1871)
  • Proposed early ideas about common descent and transformation over time (Buffon-era influence and later Vestiges concept).

Common Descent, Homology, and Homoplasy

• Common descent: Existence of shared ancestry among structures or genes in different taxa.
  • Example: Humerus, Radius, Ulna, Carpals, Metacarpals, Phalanges across HUMAN, CAT, WHALE, BAT show homologous arrangement.
• Homology vs Homoplasy:
  • Homology: traits derived from a common ancestor.
  • Homoplasy: traits that arise independently in separate lineages (convergent evolution) and are not evidence of common ancestry.

Lamarck (1744–1829) and Early Evolutionary Frameworks

• Jean-Baptiste Lamarck: Orthogenesis – driving force toward increasing complexity; evolution as directed rather than random.
• Inheritance of acquired characteristics: Acquired traits can be passed to offspring (controversial and largely unsupported by modern genetics).
• Lamarck’s two-law framework (simplified):
  • Law 1: Use and disuse strengthen or weaken organs based on sustained use; disuse leads to deterioration.
  • Law 2: Traits gained or lost due to long-term use/disuse are passed to offspring (assuming they are common to both sexes).
• Visual schematic: progressive stretching of the neck in a hypothetical ancestor leading to a longer-necked lineage (illustrating the adaptive and complexifying forces).

Critical Evaluation of Lamarck

• Key questions:
  • What mechanism explains persistent changes across generations?
  • Why did Lamarck’s mechanism fail to account for inheritance at the genetic level?

Darwin and Origins of Evolutionary Theory

• Charles Darwin (1802–1882): Sought to convince others of evolution and proposed a mechanism—natural selection.
• Major influences on Darwin:
  • Uniformitarianism
  • The voyage of the HMS Beagle
  • Selective (artificial) breeding
  • Malthus’s population principles
• HMS Beagle voyage (1831–1836): Key observational period that informed Darwin’s ideas.
• Beagle finches (Geospiza spp.) as a classic example:
  • Various finch species with different beak shapes adapted to different food sources (e.g., large, medium, small ground finches; cactus finch; warbler finch; mangrove finch; woodpecker finch; etc.).
  • Demonstrated adaptive radiation and selective pressures in different islands (e.g., Cocos Island finches).
• Darwin’s concept of natural selection:
  • Variation exists within populations; some variations are advantageous in a given environment.
  • Individuals with favorable variations are more likely to survive and reproduce, passing those traits to offspring.
  • Over generations, the frequency of advantageous traits increases in the population.
• Darwin’s famous formulation (summary):
  • Variation that is slight or significant and that is profitable to an individual in its environment tends to be preserved and inherited by offspring.
  • This process drives adaptation and speciation over time.

The Theory of Natural Selection: Formal Definition and Implications

• Natural selection as a mechanism by which evolution occurs, leading to changes in allele frequencies over generations.
• Clarification: Evolution by natural selection is a theory that explains how evolution happens; evolution itself is an observed fact (change in gene frequency over time).
• Key takeaway: All evolution can be summarized as changes in allele frequencies in populations over time.

Population Theory and Growth: Malthus’s Influence

• Malthus’s Essay on the Principle of Population (1798) highlighted the tension between geometric population growth and arithmetic food supply growth.
  • Geometric growth: Exponential-like expansion, often depicted as exponential increases in population size.
  • Arithmetic growth: Linear increase in resource production.
• Malthus argued that populations tend to grow faster than the resources that sustain them, leading to competition, struggle, and differential survival.
• This insight provided a key conceptual link to natural selection: limited resources create differential reproductive success.

Darwin and Wallace: Drafting the Mechanism of Evolution

• Alfred Russel Wallace (1823–1913) independently conceived a theory of natural selection similar to Darwin’s.
• Darwin finalized and published the theory of natural selection (On the Origin of Species, 1859) with extensive supporting evidence.
• The synergy between Darwin and Wallace helped solidify natural selection as the primary mechanism of evolution.

Evidence and Illustrative Examples of Evolution

• Descent with modification: Over time, lineages accumulate changes that reflect adaptation to environments.
• Key examples include fossil records of horses and other mammals showing gradual changes in form.
  • Horse evolution example: from smaller, multi-toed ancestors to larger, single-toed modern Equus species.
  • Transitional forms include species along the lineage, such as Mesohippus, Hyracotherium, Merychippus, Pliohippus, and modern horses.
• For each fossil transition, note dates: late Eocene to Miocene to Pliocene epochs (approximate ranges provided in the slides).
• Tooth wear and development: observed enamel, dentine, and cement changes across life stages and species; informs functional morphology and diet.

Taxonomy and Systematics: Organizing Life

• Taxonomy is the classification of organisms into a system that reflects relatedness.
• Major domains and taxa (illustrative):
  • Domains: Archaea, Bacteria, Eukaryota
  • Kingdom, Phylum, Class, Order, Family, Genus, Species (binomial nomenclature: e.g., Homo sapiens).
• Example taxonomy snapshot (illustrative):
  • Ducks → Birds → Water birds → Geese; Birds → Land birds → etc. (demonstrates hierarchical grouping).
• Sample taxonomy challenges: Some groupings may be problematic or controversial when based solely on superficial similarities.

Descent with Modification: Evidence from Anatomy and Fossils

• Homology: shared ancestry indicated by similarities in structures across diverse taxa (e.g., humerus, radius, ulna, carpals, metacarpals, phalanges in human, cat, whale, bat).
• Homoplasy: traits that arise independently in separate lineages (convergent evolution), not due to shared ancestry.

Beagle Voyage: Darwin’s Observational Catalysts

• On the voyage, Darwin collected data that supported the idea that populations adapt to local environments.
• Finches on the Galápagos Islands displayed a range of beak shapes and sizes, correlating with food resources and ecological niches.
• This variation provided a tangible demonstration of natural selection in action.

Population Growth, Competition, and Selection (Connection to Malthus)

• The interplay between population growth and resource limits creates selective pressures.
• Those individuals with heritable traits that enhance survival/reproduction become more common over generations.

The Ethical Dimension: Rights and Representation in Remains Studies

• The acquisition and study of human remains raise ethical questions:
  • Who has the authority to grant access to remains?
  • How should communities be involved in decision-making?
  • Balancing scientific knowledge with respect for the dead and living communities.

Key Equations and Concepts to Memorize

• Evolution definition (genetics-focused):
  • Change in allele frequency within a population over time. Let pt be the frequency of allele A at time t, qt = 1 - p_t be the frequency of allele a.
  • Change in allele frequency: riangle p = p{t+1} - pt
• Geometric vs. arithmetic growth (Malthus):
  • Geometric growth: Nt = N0 imes ext{growth factor}^t
  • Arithmetic growth: Nt = N0 + r t
• Stratigraphy time scale (selected anchors):
  • Holocene ≈ 10{,}000 ext{ years ago to present}
  • Cenozoic era includes Paleogene, Neogene, and Quaternary periods
  • Paleocene (≈ 65.5 Ma) → Eocene (≈ 55.8–33.9 Ma) → Oligocene (≈ 33.9–23.0 Ma) → Miocene (≈ 23.0–5.3 Ma) → Pliocene (≈ 5.3–2.6 Ma) → Pleistocene (≈ 2.6 Ma–11.7 ka) → Holocene (11.7 ka–present)
• Descent with modification (conceptual):
  • More recent descendants differ from their ancestors due to accumulated heritable changes.
  • Evidence includes fossil series (e.g., horses), comparative anatomy (homologies), and genetic data (not shown in slides but foundational).

Connections to Foundational Principles and Real-World Relevance

• How the history of anthropology informs current practice:
  • Critiques of racial typologies and the move toward cultural relativism (Boas) and biological anthropology that emphasizes population variation and clines rather than discrete races (contrast Blumenbach, Morton).
• Evolution as a unifying framework across biology: genetics, paleontology, anatomy, and ecology.
• Ethical stewardship in research: respecting the rights and beliefs of descendant communities when studying human remains and cultural artifacts.

Practical and Philosophical Implications

• The shift from typological racial thinking to population biology mirrors broader shifts toward empirical testing, evidence-based conclusions, and humility about human diversity.
• The interplay between science and society: how research practices, representation, and ethics influence what is studied and how findings are shared with the public.
• The importance of multiple lines of evidence (fossil record, comparative anatomy, embryology, genetics) in building robust evolutionary theories.

Reminders and Next Steps (Class Logistics)

• Next Class:
  • Check-in Question due at 3pm on Thursday.
  • Multi-media assignment #1 due at midnight.
• Multi-media Analysis #1 Details (due August 28th, at Midnight).

Summary: Core Takeaways

• Evolution is observed as changes in allele frequencies within populations over time, with natural selection as a central mechanism.
• Early thought linked human variation to fixed racial types, but later work (Boas, Hooton, Hrdlička, Washburn) reframed the discussion toward population biology, adaptation, and culture.
• Darwin and Wallace provided a cohesive mechanism—natural selection—based on variation, differential survival, and reproduction, enriched by Malthus’s insight on population pressure.
• Pre-Darwinian thinkers (Buffon, Erasmus Darwin, Chambers) contributed to the lineage of ideas about descent and change, though without a unifying mechanism.
• The study of human remains raises important ethical questions about consent, ownership, and the rights of descendant communities in scientific research.

Practice Prompts (for exam preparation)

• Explain the difference between homology and homoplasy with an example.
• Describe how uniformitarianism and stratigraphy contribute to understanding evolutionary timescales.
• Outline Lamarck’s two laws and discuss why they are not supported by modern genetics.
• Summarize the Beagle voyage’s significance for Darwin’s development of natural selection, using the finches as an example.
• State Malthus’s geometric vs. arithmetic growth and explain how this concept feeds into natural selection.